Heating cable for extraction pipes of viscous hydrocarbons or paraffinic in conventional wells and type tight wells, vertical or directional, with  flooded annular in casual or permanent form, suitable for use between low and high fluid pressures ranges

ABSTRACT

The present invention relates to a heating cable for extraction pipes of viscous hydrocarbon or paraffinic in conventional wells and tight type wells, with flooded ring in eventual or permanent cases, suitable for use between low and high fluid pressure ranges. The cable, flat type with parallel electric conductors, is also suitable for use in both vertical and directional wells with high operational flexibility in a wide range of variables. Each of the electric conductors ( 2 ) is covered by a primary insulation layer ( 3 ), and the set of conductors is monolithically coated by a main insulating layer ( 4 ) made of fluoropolymer material resistant to the high pressure of the surrounding fluid. Outside of the main insulating layer ( 4 ), the structure of the cable is complemented with an external shield ( 5 ) defined by a thin metallic material layer.

FIELD OF THE INVENTION

The present invention relates to a heating cable for extraction pipes of viscous hydrocarbon or paraffinic in conventional wells and tight type wells, vertical or directional, with flooded annular in eventual or permanent cases, suitable for use between low and high fluid pressure ranges, the cable being flat with parallel electric conductors, with high operational flexibility.

The purpose of this heating type cable is to avoid and/or unblock obstructions in extraction well pipes for hydrocarbons caused by the accumulation of substances, such as paraffin and hydrates, as well as to reduce the high oil viscosity rates, hindering the fluid removal, especially when this fluid is at the lower paraffin viscosity or precipitation temperature values, lower than the suitable limit values, and exposed to high pressure, for example, over a 1000 psi and reaching more than even the 10,000 psi.

STATE OF THE TECHNIQUE AND PROBLEMS TO SOLVE

The WO 92/08036 document discloses a special heating cable in which the heating effect is achieved by a short circuit between the core and one of the surface layers.

The WO 00/11317 document discloses a heating cable which includes fiber optic conductors. The fiber optic allows measuring the well's temperature; and therefore, it is also used to detect fluid presence by the temperature difference.

The U.S. Pat. No. 5,782,301 document refers to a heating cable whose structure is predominantly made of lead, intended to the three-phase power supply which is applied directly on the pipe. In the practice, this type of cable has resulted in numerous faults, only tolerated low heating powers and required very high currents, therefore they are not suitable for oil production pipes of high viscosity or pressure.

The U.S. Pat. No. 5,065,818 document refers to a heater that is fixed onto the concrete walls of non-intubated wells.

The U.S. Pat. No. 4,911,239 document refers to a heat pump, which heats the intake making a short circuit between the pumping tree and the wall of the tube production.

Finally, it is worthy to mention the Utility Model AR039993B4, referred to a heating cable for oil production pipes characterized because it includes the combination of a thermo conductive metal outer pipe and inner flexible cover with electrically insulating properties, anti-corrosive and mechanical strength properties, wherein the cover is formed by a plurality of overlapped layers which includes: (a) first an electrically insulating inner layer which surrounds the power electrical wires for the heater elements connected to the conductor along the device; (b) a second enmeshing metallic layer that surrounds the first layer; (c) a third polymeric layer that surrounds the second layer; and (d) an outer shielding layer, which surrounds the third layer. Although this heating cable, under certain conditions, properly meets its function, when it is subjected to high pressures inside of the hydrocarbon production well, begins to have structural and functional deficiencies. It is to say, through the interstices of the metallic mesh, the high pressure causes deformation in the insulating layer that surrounds the electrical conductors, thus affecting the dielectric capacity of the insulation layer, which results even more noticeably by the chemical effects of the fluid that is filtered between the mesh and the insulating layer. In addition, the metallic mesh is permeable to the radio frequencies, which, due to their own flow current can generate interference on other cables or instruments used in the well.

With the current state of technology, it is common that the wells are brought to exploitation limits that were before impossible, and is usual that the wells are of high pressure, for example, the tight type of wells of recent development in the world. All of this leads to all accessories and elements used in the extraction should be more resilient, so it is essential that the development of new elements are highly resistant to high pressure and temperatures, as is the cable that is the object of the present invention.

Advantageous of the Invention

In the heating cable of the present invention, the number of layers that define its structure with regard to the succession of layers of the conventional cables has been reduced, allowing to simplify the manufacturing process, lowering the time than the standard time involved, and reducing the electric energy consumption of the required materials or supplies, all of which translates into lower cable manufacturing cost. Regarding the advantages in the use of this cable, it is worth mentioning, for example, that it is extremely suitable to withstand high pressure and temperatures without risk of leakage between the layers that could damage its structure, such as is the case in conventional cables, thus, increasing the cable service life, and maintaining the electrical conductors insulated efficiently and protected even in the presence of very high fluid pressure. The novel monolithic structure in this type of fluoropolymer materials gives this cable a great mechanical resistance to the compression and, at the same time, a high dielectric coefficient without fissures, which gives a high reliability and a wider range of operation. Also, these structural features provide a greater resistance to reinstallation operations arising from “pulling” operations, usually in wells and particularly critical in horizontal or directional wells by high mechanical exposure of them.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a heating cable for extraction pipes of viscous hydrocarbon or paraffinic in conventional wells and tight type wells, vertical or directional, with flooded ring in eventual or permanent cases, suitable for use between low and high fluid pressure ranges. This cable, of flat type with parallel electric conductors, is also suitable for use in both vertical and directional wells, with high operational flexibility in a wide range of variables. Each one of the electric conductors is covered by a primary insulation layer, and the assembly thereof is monolithically coated by a main insulating layer of fluoropolymer material resistant to the high pressure of the surrounding fluid. Outside of the main insulating layer, the cable structure is complemented with an external shield defined by a thin layer of metallic material.

BRIEF DESCRIPTION OF THE DRAWINGS

For greater clarity and understanding of the present invention, it is illustrated in several figures where it is represented according to the preferred embodiments, for example, where:

FIG. 1 is a cross-sectional view of the heating cable.

FIG. 2 is a partial cross-sectional perspective view of a section of the heating cable.

FIG. 3 shows, as an example of application of the heating cable, a section of the hydrocarbons extraction pipe on which are fixed the thermo conductive conductors in which interior extends the cable.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1 and 2 can be seen that the heating cable object of the present invention, designated with the general reference number 1, is a flat cable which presents lines of electrically conductive conductors 2 parallel to each other, each one of which is covered by a primary insulation layer (3). The conductor set (2) is monolithically coated by a main insulating layer (4) of fluoropolymer material which is resistant to the high pressure of the surrounding fluid. Outside this main insulating layer, the structure of the cable is complemented by external shielding (5) defined by a thin layer of a metallic material which, by example, can be defined by a ribbon placed by following a spiral wrapping form.

On the example of the preferred embodiment, which is described and illustrated, the electrical conductors 2 are of the multifilament type, and the cable 1 includes three lines of conductors 2 which correspond to each one of the phases of the three-phase power applied.

FIG. 3 shows a typical hydrocarbons extraction pipe 6 which is placed in a production well, on which are fixed, heat exchangers and thermo conductive metallic conduits 7, through support devices having anchors 8 and clamps 9. Throughout the conduits 7, the heating cable 1 of the present invention is extended.

Optionally, according to an alternative use of the cable 1, in the practice, the thermo conductive conduits 7 can be attached, for example, to a rod located in the interior of the production pipe 6 in position substantially coaxial with the mounting and fastening devices. In this way, the thermo conductive conduits 7 with the cable 1 inside, will define a direct heat exchange medium with the fluid transported by the production pipe, it is worthy to say that without the duct 5 being in contact with the inner wall of the production pipe, but directly with the circulating fluid within it.

Having thus particularly described and determined the nature of the present invention and how it is to be realized, is claimed, in exclusive the right and property. 

1-9. (canceled)
 10. A heating cable for extraction pipes of viscous hydrocarbon or paraffinic comprising: a cable; a set of electric conductors located inside the cable; a first insulating layer surrounding each one of the electric conductors; a monolithically layer made of fluoropolymer material surrounding the set of electric conductors; and a metallic shield surrounding the cable.
 11. The heating cable according to claim 10, wherein the cable is flat.
 12. The heating cable according to claim 10, wherein the electric conductors are multifilament electric conductors.
 13. The heating cable according to claim 10, wherein the set of electric conductors includes three electrical conductors.
 14. The heating cable according to claim 10, wherein the metallic shield is a thin layer, the metallic shield is wrapped on the cable in a spiral form. 